ANSWER:
Not every Imam is a person of knowledge or a person that one can learn from! There are a lot of ignorant people assuming the positions of Imams! There are a lot of such Imams especially in Europe and USA who follow their desires and what the masses want.
Boxing and MMA are prohibited as it involves hitting the face. Celebrating this man’s victory just because he is a Muslim is like celebrating having a Muslim female sprinter winning the Olympics! There is nothing to be proud of!